How to Tell If You Have The Flu or COVID-19

Learn about the different symptoms of COVID-19 and the flu as well what to do when you start feeling sick.

As fall approaches, so too does the start of the flu season. But unlike other years, this season comes as the U.S. continues to fight the spread of another contagious respiratory illness: COVID-19. Complicating matters is the fact that both illnesses share similar symptoms, making it difficult to distinguish one from the other. Understanding the similarities and differences between COVID-19 and the flu can help you better prepare and protect yourself this fall. Here’s what you need to know to stay healthy:

The Symptoms

Both COVID-19 and the flu can vary in terms of degree and severity of symptoms from person to person. Some may have more severe cases of these illnesses, while others may be completely asymptomatic. Shared symptoms of both the flu and COVID-19 include the following:

  • Fever or feeling feverish/chills
  • Cough
  • Shortness of breath or difficulty breathing
  • Fatigue
  • Sore throat
  • Runny or stuffy nose
  • Muscle pain or body aches
  • Headache
  • Some people may have vomiting and diarrhea, though this is more common in children than adults

Unlike the flu, however, some people with COVID-19 may experience new loss or taste or smell. Additionally, while flu is associated with a more rapid onset of symptoms, one to four days after infection, symptoms of COVID-19 may take between 2 to 14 days to develop. Typically, a person starts showing symptoms 5 days after being infected.


COVID-19 and the flu are both spread from person-to-person, between people who are in close contact with one another (within about 6 feet). Both viruses are spread through respiratory droplets when an infected person coughs, sneezes, or talks or by touching a surface with the virus on it and then touching the eyes, nose or mouth without washing hands. Similarly, both the flu virus and the virus that causes COVID-19 may be spread to other people before symptoms develop.

COVID-19, however, is believed to be more contagious than the flu and involved in more “superspreading events” where one person infects many others. Likewise, people with COVID-19 may be contagious for longer than those with the flu. According to the CDC, most people with the flu are contagious about 1 day before showing symptoms. Older children and adults with flu appear to be most contagious during the initial 3-4 days of their illness but many remain contagious for about 7 days. Meanwhile, those with COVID-19 may be contagious for 2 days before showing symptoms and remain contagious for at least 10 days after symptoms appear or testing positive, and even longer for people with more severe cases.

High Risk

While most cases of both COVID-19 and flu are mild, both cause a variety of severe illnesses or complications. Complications from both viruses include the following:

  • Respiratory failure
  • Cardiac injury (e.g. heart attacks and stroke)
  • Multiple-organ failure (respiratory failure, kidney failure, shock)
  • Worsening of chronic medical conditions (involving the lungs, heart, nervous system or diabetes)
  • Secondary bacterial infections (i.e. infections that occur in people who have already been infected with flu or COVID-19)

While everyone is at risk of both COVID-19 and flu, adults 65 and older and people with underlying medical conditions are at higher-risk of severe illness or complications from infection. Pregnant women may also be at increased risk of illness and hospitalization from both viruses. Though children may not be at higher risk of catching either flu or COVID-19, research is showing that healthy children are at higher risk of complications from flu than COVID-19. Kids with COVID-19 are also at higher risk of Pediatric Multisystem Inflammatory Syndrome, which is most likely rare.


The NeuMed blog is published by NeuMed Modern Urgent Care + IV Therapy, an innovative urgent care and IV infusion therapy clinic with locations in Houston, Texas.

Any general advice posted on our blog, or website is for informational purposes only and is not intended to replace or substitute for any medical or other advice. If you have specific concerns or a situation arises in which you require medical advice, you should consult with an appropriately trained and qualified medical services provider.